An image forming apparatus is an apparatus that forms an image on a printing medium according to input signals. Examples of the image forming apparatus include printers, copiers, facsimiles, devices combining some or all functions thereof, and the like.
Broadly speaking, in an electro-photographic type image forming apparatus as one type of image forming apparatus, light is irradiated on an image carrier charged with a predetermined electric potential, to form an electrostatic latent image on a surface of the image carrier. As a developer is fed to the electrostatic latent image, a visible image is formed on the image carrier. The visible image formed on the image carrier is transferred to a printing medium directly or by way of an intermediate transfer member. The image transferred to the printing medium is fixed to the printing medium via a fixing process.
The developer, to be attached to the image carrier so as to produce an image, is received in a developer cartridge. The developer, received in the developer cartridge, is delivered by a developer delivery unit provided in the developer cartridge, and is fed to a developing unit through a feed hole perforated in the developer cartridge.
The developer delivery unit, which may be provided adjacent to the feed hole of the developer cartridge, includes a delivery member to deliver the developer via rotation thereof. The amount of the developer, which is attached to and delivered by the delivery member, may depend upon, for example, the rotating speed of the delivery member and the degree of interference between the delivery member and the contact portion of a receiving member that is used to receive the delivery member.
The contact portion comes into contact with a surface of the rotating delivery member, and separates the developer from the delivery member. The greater the interference between the delivery member and the contact portion, the greater the amount of the developer separated from the surface of the delivery member, causing a greater amount of the developer to be delivered.
The developer separated from the delivery member by the contact portion is discharged from the developer cartridge through the feed hole, and the discharged developer is fed to a developing roller that applies the developer to the image carrier.
As described above, to increase the amount of the developer to be fed, it is necessary to increase the interference by the contact portion that is used to separate the developer attached to the surface of the delivery member.
Conventional image forming apparatuses have attempted to forcibly press the contact portion toward the delivery member in order to increase the amount of the developer to be separated. While such forcible pressing contact may increase the interference, resulting greater separation of the developer from the surface of the delivery member, and consequently, an increased amount of the developer fed, the increased contact pressure may also increase the likelihood of abrasion of, and damage to, the surface of the delivery member.
During operation, the delivery member repeats rotation and stoppage according to the variation in the amount of the developer supplied to the image carrier. The forcible pressing of the contact portion toward the surface of the delivery member may unfortunately also increase the starting load on rotation of the delivery member to an undesirable level.